The Effect Of Fictive Temperature On Nano-tribological Behavior Of Bulk Metallic Glass

Metallic glasses are widely used in industrial,transportation,aerospace,military,and medical fields due to their attractive properties,such as large elastic limit,high strength,superior wear resistance,excellent soft magnetic properties and outstanding biocompatibility,which are related to its unique amorphous structure.However,the disordered amorphous structure makes it difficult to establish the relationship between the nanotribological properties of metallic glasses and their structures,which hindering the design and preparation of metallic glasses with excellent properties.To this end,in this paper,bulk Zr-based metallic glasses with fictive temperatures of 320 °C,370 °C,and 410 °C were prepared,and the relationship between the fictive temperature and the free volume of the metallic glass was established.Then,we investigate the effect of structure on nanomechanical and nanotribological properties of metallic glasses via the nanoindentation\scratch tests.The specific content and conclusions are as follows:(1)The nanomechanical properties of metallic glasses are related to their structure.In the nanoindentation experiment,this article investigated the relationship between the structure of metallic glass and nanomechanical properties based on nanoindentation experiments.The results show that with the increase of the fictive temperature from 320 ? to 410 ?,the nano hardness of the metallic glass decreases by 6.6 %,the reduced modulus decreases by 5.4 %,and the elastic recovery ability of the indentation decreases by 1.3 %.This is due to the large free volume and loose atomic arrangement of metallic glasses at high a fictive temperature,which provide more sites for the formation of shear transition regions and shear bands,and the plastic deformation ability of metallic glasses increases,which eventually leads to low Nano-hardness combined with elastic recovery.Furthermore,we found that the plastic deformation of metallic glasses is different from the pop-in events,which provides strong evidence for the theory of homogeneous plastic flow in metallic glasses.(2)The nanotribological properties of metallic glasses are related to their structure and friction mechanism.This article explored the relationship between nanotribological behavior and structure of metallic glass based on nanoscratch experiments.The results show that with the fictive temperature increases from 320 ? to 410 ?,the depth of scratches on metallic glass increases and the wear resistance decreases,which is related to the structure of metallic glass.However,the friction coefficient of metallic glass is not only related to the structure of the metallic glass,but also to the friction mechanism.Under small loads,the friction coefficient of metallic glass is determined by the adhesive friction mechanism,which is related to the sample atomic density and the strength of asperities.Since the metallic glass with a fictive temperature of 320 °C has a higher atomic density and stronger asperity peaks,which increases the interfacial shear strength between the needle tip and the metallic glass surface,the friction coefficient is the largest in the no-wear friction stage.Under a larger load,the friction coefficient of metallic glass is related to the plowing friction mechanism.Because the plowing model between cube corner tip and plane is established by us shows that the plowing friction coefficient of metallic glass is inversely proportional to its elastic recovery,the metallic glass with a fictive temperature of 410 °C leads to a high friction coefficient due to its low elastic recovery.